Method for hardening the surface of a component in a wind turbine

ABSTRACT

A method for hardening a surface of a component in a wind turbine is disclosed. The component to be hardened includes a surface and the surface is applied with a blasting material by ultrasound waves. The component is a part of a drive or a drive housing, a bearing surface, a gear wheel or a pinion. The ultrasound waves are emitted with the aid of a piezo electric transducer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German application No. 10 2010 006094.1 filed Jan. 28, 2010, which is incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

The present invention relates to a method for hardening the surface of acomponent in a wind turbine, in particular the surface outer layer of acomponent in a wind turbine.

BACKGROUND OF THE INVENTION

Microscopic cracks in the respective part frequently appear, as a resultof high Hertzian pressure, in heavily loaded regions of drives, forinstance in heavily stressed regions of bearing surfaces of drives ortooth flanks of gear wheels. Microscopic cracks of this type may resultin premature faults and corresponding failures of the respective part.The crack formation frequently occurs on the outer surfaces and/or inthe region of the periphery of the heavily loaded contact surfaces.Micro defects of this type reduce the operating time and the servicelife of the respective part, for instance of the drive and the drivehousing. In numerous plants, for instance in wind turbines, the thusnecessary replacement of the respective component, for instance of thedrive or parts thereof, is generally complicated and expensive.

The hardening processes and processing technologies used to date, suchas rolling, hard turning or blasting material peening, do not achieveincreased internal stress particularly of the heavily loaded contactregions and therefore reduce the high tensile load. Only internalstresses of a maximum of 400 MPa can currently be achieved.

DE 10 2007 009 470 A1 and WO 93/20247 A1 describe methods for thesurface peening, in particular for the ultrasound ball peening of apart, in particular a gas turbine. Ultrasound blasting material peeningis characterized in that a sub-region of the surface of a part ishardened by applying a blasting material. The blasting materialpreferably consists of small balls with a diameter of less than 4 mm.

SUMMARY OF THE INVENTION

The object of the present invention consists in providing anadvantageous method for hardening the surface of a component in a windturbine. This object is achieved by a method as claimed in theindependent claim. The dependent claims contain further advantageousembodiments of the invention.

The inventive method for hardening the surface of a component in a windturbine is characterized in that the component to be hardened has asurface and the surface is applied with a blasting material by means ofultrasound waves. The component to be hardened can be in particularparts of bearings or the drive of the wind turbine. In particular, thecomponent can include a part of a drive or a drive housing, a bearingsurface, in particular of a bearing, for instance a bearing surface of aroller bearing, or of a drive, a gear wheel or a pinion, in particular adrive pinion. The component to be hardened can be in particular a toothflank of a gear wheel.

By means of ultrasound blasting material peening, in other wordsapplying the surface to be hardened with a blasting material by means ofultrasound waves, the internal stress of the respective component isincreased and the susceptibility to cracking is thus reduced. Theservice life and the operating time of the respective component areincreased in this way by approximately 20%.

The ultrasound waves can preferably be emitted with the aid of a piezoelectric transducer. For instance, ultrasound waves can be emitted witha frequency between 10 kHz and 30 kHz, preferably 20 kHz. It isparticularly advantageous if the ultrasound waves are amplified. Thiscan take place for instance with the aid of an acoustic amplifier.

The blasting material can preferably include a relatively heavymaterial, like for instance tungsten carbide, and/or consist of tungstencarbide. In addition, the blasting material can include balls. Theblasting material can preferably include balls with a diameter of morethan 1 mm, advantageously with a diameter of more than 5 mm, or canexclusively consist of blasting balls with a diameter of more than 1 mm,advantageously with a diameter of more than 5 mm. It has emerged thatthe use of tungsten carbide balls and the use of balls with a relativelylarge diameter, in particular of more than 5 mm, can achieveparticularly high internal compressive stress results, since the ballsare in this case embodied in a relatively large and heavy fashion.

With the aid of the inventive method, internal stresses, in particularof bearing surfaces of wind turbine bearings and wind turbine drives,for instance gear wheel drive systems, of more than 800 MPa can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, characteristics and advantages of the presentinvention are described in more detail below with reference to anexemplary embodiment with respect to the appended figures. Here thedescribed features are advantageous both individually and also incombination with one another.

FIG. 1 shows a schematic representation of a wind power plant.

FIG. 2 shows a schematic representation of a first cross-section througha part of an apparatus for implementing the inventive method on a gearwheel.

FIG. 3 shows a schematic representation of a second cross-sectionthrough a part of an apparatus for implementing the inventive method ona gear wheel.

FIG. 4 shows a schematic representation of a first cross-section througha part of an apparatus for implementing the inventive method on theinterior surface of a roller bearing outer ring.

FIG. 5 shows a schematic representation of a second cross-sectionthrough a part of an apparatus for implementing the inventive method onthe inner surface of a roller bearing outer ring.

FIG. 6 shows a schematic representation of a first cross-section througha part of an apparatus for implementing the inventive method on theouter surface of a roller bearing inner ring.

FIG. 7 shows a schematic representation of a second section through apart of an apparatus for implementing the inventive method on the outersurface of a roller bearing inner ring.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the invention is described in more detailbelow with the aid of FIGS. 1 to 7. FIG. 1 shows a schematicrepresentation of a wind power plant 1. The wind power plant 1 includesa tower 2, a pod 3 and a rotor hub 4. The pod 3 is arranged on the tower2. The rotatably mounted rotor hub 4 is arranged on the pod 3. At leastone rotor blade 5 is fastened to the rotor hub 4. The wind power plant 1typically includes two or three rotor blades 5.

The wind power plant 1 also includes at least a rotational axis 6, amain bearing 30, a drive 7, a brake 8 and a generator 9. The rotationalaxis 6, the main bearing 30, the drive 7, the brake 8 and the generator9 are arranged inside the pod 3. A center to center difference isessentially possible in the drive 7. Different components can thereforehave different rotational axes. In addition, the wind power plant 1 canalso be embodied without drives.

FIG. 2 shows a schematic representation of a cross-section through partof an apparatus for implementing the inventive ultrasound shot peeningmethod. The apparatus includes a peening chamber 10, within which theshot peening is implemented. Part of a component to be hardened, in thepresent exemplary embodiment part of a drive pinion 11, is arrangedwithin the peening chamber 10. The drive pinion 11 includes a rotationalaxis 13. FIG. 2 shows a cross-section through the drive pinion 11 alongthe rotational axis 13, in other words an axial cross-section. The drivepinion 11 includes a number of teeth 24, of which at least one part isarranged within the peening chamber 10. The surface to be hardened ofthe teeth 24 of the gear pinion 11 is identified with referencecharacter 26.

At least one part of a sonotrode 17 is also arranged within the peeningchamber 10. The sonotrode 17 is preferably arranged opposite the surface26 to be hardened. The sonotrode 17 is connected to an amplifier 16,preferably an acoustic amplifier. The amplifier 16 is also connected toa transducer, preferably in the form of a piezo electric emitter.

A cavity 27 is disposed between the sonotrode 17 and the drive pinion 11within the peening chamber 10. A number of balls 18 are arranged in thiscavity 27. The balls 18 preferably consist of tungsten carbide. Theballs 18 advantageously have a diameter of more than 1 mm, preferably ofmore than 5 mm. A homogenous hardening of the surface 26 is herewithachieved.

In order to implement the inventive method, ultrasound waves with afrequency between 30 kHz and 10 kHz, advantageously with a frequency of20 kHz, are generated with the aid of the transducer 14. The ultrasoundwaves are then amplified with the aid of the acoustic amplifier 16. Theamplified ultrasound waves are transmitted by means of the sonotrodeinto the peening chamber 10, and/or into the cavity 27 disposed therein.The ultrasound waves cause the balls 18 inside the peening chamber 10 tovibrate and move inside the peening chamber 10. The balls 18 are in thisway reflected by the surface of the sonotrode 17, by the surface 26 tobe hardened and by the walls of the peening chamber 10. In addition, theballs 18 collide with one another. As a result of the random scatteringof the balls 18, a homogenous treatment of the surface 26 to be hardenedis achieved.

FIG. 3 shows a schematic representation of a cross-section according toFIG. 2 through an apparatus for implementing the inventive method.Contrary to FIG. 2, the drive pinion 12 is shown in FIG. 3 in a radialcross-section, in other words in a cross-section at right angles to therotational axis 13. The view of the remaining parts in FIG. 3 canessentially correspond to the cross-section shown in FIG. 2, with onlythe part 11 and/or 12 to be hardened being arranged differently.Alternatively the cross-section shown in FIG. 3, in respect of allparts, may be a cross-section at right angles to the cross-section shownin FIG. 2. The longitudinal axis of the apparatus is identified in bothFIGS. 2 and 3 with reference character 15.

The teeth 24 of the drive pinion 12 shown in FIG. 3 include tooth flanks25. With the aid of the inventive method, the tooth flanks 25 can inparticular be effectively hardened, since as a result of the randomscattering of the balls, the whole surface to be hardened can be evenlytreated.

FIGS. 4 and 5 show a cross-section through part of an apparatus forimplementing the inventive method. FIGS. 4 and 5 show the hardening ofthe inner bearing surface 21 of a roller bearing outer ring 19 and/or20. Here the roller bearing outer ring 19 in FIG. 4 is shown in an axialcross-section in respect of a rotational axis 23. FIG. 5 shows theroller bearing outer ring 20 in a radial cross-section in respect of therotational axis 23. Similarly to the embodiments rendered in conjunctionwith FIGS. 2 and 3, FIGS. 4 and 5 may be two cross-sections arranged atright angles to one another and the same arrangement or however the samecross-section, with the roller bearing outer ring 19 and/or 20 beingarranged differently.

The same applies to FIGS. 6 and 7, in which a cross-section is shownthrough an apparatus for hardening the outer bearing surface 22 of aroller bearing ring 28 and/or 29. FIG. 6 shows part of the rollerbearing inner ring 28 in an axial cross-section in respect of therotational axis 23, while FIG. 7 shows part of the roller bearing innerring 29 in a radial cross-section in respect of the rotational axis 23.

The inventive method described in conjunction with FIG. 2 can beimplemented in a similar fashion with the aid of the embodiments shownin FIGS. 3 to 7.

As a result, an internal stress of the surface of the drive pinion 11,12, in particular of the surface of the tooth flanks 25, of the outerbearing surface 22 and of the inner bearing surface 21 of the rollerbearing ring 19, 20, 28, 29 of more than 800 MPa can be achieved withthe aid of the inventive method.

1.-9. (canceled)
 10. A method for hardening a surface of a component ina wind turbine, comprising: applying a blasting material by ultrasoundwaves with the surface of the component.
 11. The method as claimed inclaim 10, wherein the component is a part of a drive or a drive housing,a bearing surface, a gear wheel or a pinion.
 12. The method as claimedin claim 10, wherein the ultrasound waves are emitted by a piezoelectric transducer.
 13. The method as claimed in claim 10, wherein theultrasound waves are emitted in a frequency between 10 kHz and 30 kHz.14. The method as claimed in claim 10, wherein the ultrasound waves areamplified.
 15. The method as claimed in claim 10, wherein the blastingmaterial comprises a tungsten carbide.
 16. The method as claimed inclaim 10, wherein the blasting material comprises a ball.
 17. The methodas claimed in claim 10, wherein the ball has a diameter of more than 1mm.
 18. The method as claimed in claim 17, wherein the ball has adiameter of more than 5 mm.